Minimally invasive surgery (MIS), also referred to as laparoscopic or endoscopic surgery, has experienced spectacular growth worldwide over the past few decades for the diagnosis and treatment of a variety of acute and chronic pathologies. Endoscopic procedures are economical, safer, and promote a more rapid recovery in contrast to conventional surgical approaches. Technological advancements in MIS are expected to have robust growth in the future. As endoscopic technologies develop and become the standard of care for most types of surgical interventions, the continued development of innovative quality tools to address the unique problems associated with this type of surgery must be vigorously pursued.
A laparoscopic surgery is performed by inserting a cannula (a hollow plastic or metal tube) through the abdominal wall, either by scalpel dissection or by blunt penetration with a piercing instrument (a trocar) occupying the central lumen of the cannula. When the cannula is placed through the skin and into the abdomen, the surgical blade or central trocar is withdrawn, leaving a cannula that is designed to inflate the abdominal cavity with carbon dioxide gas in order to distend the anterior abdominal wall away from the internal organs. The presence of this gas in the abdominal cavity is known as a pneumoperitoneum.
Once the pneumoperitoneum is established, a fiber optic endoscope (which may either be attached to a high-definition video camera or guided by direct vision) is inserted safely into the abdomen allowing visualization of the abdominal viscera. When complete visualization of the abdomen is accomplished, a number of secondary cannulae are placed via the previously described technique. The surgery is then performed through these cannulated passageways, referred to as ports. The ports function as conduits for the insertion and exchange of various specialized hand-held or robotic-assisted instruments and devices to accomplish the laparoscopic procedure, which would otherwise be performed by an open surgical incision.
The observed benefits of MIS include reduced blood loss, lower risk of infection, more rapid recovery rates, and reduced postoperative pain. These benefits have caused laparoscopy to become the preferred method for an ever-increasing number of surgical procedures. As with any other surgery, however, MIS is not without its share of complications. Two common complications relevant to MIS surgeries are the formation of abdominal adhesions and/or hernia development.
While laparoscopic adhesion formation occurs less frequently than those related to open surgeries, the risk remains omnipresent as a result of the cumulative effect of the fibrin-forming inflammatory process. Factors that predispose the development of adhesions include: ischemia (poor blood supply), obesity, malnutrition, diabetes, or the devascularization of the peritoneum caused by the surgery itself. The development of adhesions generally occurs between the fifth and seventh postoperative day, resulting in scar-like bands. These adhesive bands may surround the intestine and adhere them either together, or to the peritoneum of the interior abdominal wall. However, months to years later after the initial surgery, these constrictive bands may form a thickened fibrous web which, when fully compact, are capable of inflicting severe pain or causing an intermittent-to-complete bowel obstruction. These two unfortunate scenarios will likely translate into higher medical costs related to emergency surgical procedures, lengthy hospital admissions, and prolonged recovery periods.
The other complication related to minimally invasive procedures is the port-site wound hernia, also referred to as an incisional or ventral hernia. The port-site wound hernia is defined as the abnormal protrusion of abdominal viscera through the wound's fascial defect. This type of hernia commonly develops in the first four years after the index surgery. At present, there is a problematic lack of long-term data on the incidence and natural history of port-site hernia development. Significant contributing factors for port-site wound herniation relate to the size and location of the fascial defect.
Obese patients, with a body mass index (BMI) of thirty or greater, are more susceptible to port-site wound herniation regardless of the fascial defect's size. This may be attributed to the obese patient's enlarged pre-peritoneal space and/or tendency toward elevated intra-abdominal pressures. Extensive manipulation and stretching of the instrument port during the MIS procedure (i.e. retrieval of specimens, multiple re-insertions, or aggressive use of laparoscopic instruments or devices) may enlarge the size of the fascial defect beyond the wound's initial diameter thus rendering the fascial defect vulnerable to port-site wound herniation.
With regards to location, herniation occurs more frequently when the fascial defect is located in the midline of the abdomen, especially in the upper midline area or at the umbilicus, possibly due to the absence of supporting musculature in these areas. In contrast, port-site wound hernias occur less often when they are located below the umbilicus or more laterally on the abdomen.
Another contributing factor for the development of a port-site wound hernia is known as the Chimney Effect. This describes a partial vacuum that is created as the surgical cannula is withdrawn from the wound, much like a piston. As this negative pressure increases within the narrow perimeter of the wound, it is capable of drawing abdominal viscera through the fascial defect and in the subcutaneous tissue or out of the body, thus creating the port-site wound hernia.
There are two technical risk factors for port-site wound hernia: the surgical trocar design used for creating the wound, and/or the suture used for closing the fascial defect. With regards to the former, the bladed trocar presents a greater risk for port-site wound hernia development than non-bladed trocars. Port-site wound herniation may also be related to the repair of the fascial defect with suture, as exemplified by suture fractures, slipping of suture knots, excessive suture tension, or sutures that absorb too rapidly. Suture closure of these wounds can be time consuming and difficult whether the suturing method is performed by the traditional approach (a needle attached to a suture and operated by a needle holder held in the operator's hand), or by a contemporary method using wound closure devices. The latter generally incorporates a needle or sharp tool with a suture affixed to one end in order to approximate and close the fascial defect.
Regardless of the method, the application involves the same time-consuming and cumbersome approach for employing a needle (or sharp tool) with a suture affixed to one end in order to approximate and close the fascial defect within the narrow recesses of the port-site wound. Moreover, these suture techniques have the predictable risk of injuring the underlying bowel, omentum, or other organs as the needle is swept through the fascial tissues.
In obese patients these suturing methods can be painstakingly difficult, since the fascia is obscured from view by adipose tissue. If the fascial defect is too deep and/or is located at a steep angled trajectory in relation to its small skin incision, a blind attempt (e.g., with no direct vision) is the only option for closing the fascial defect. This risky suturing effort generally fails to capture a sufficient margin of the wound's edge.
With regards to the contemporary devices, they may share the same vexing difficulties as the traditional method. However, a specific drawback with these devices relates to their requirement for a pneumoperitoneum and direct visualization during their surgical application. This time-consuming requirement proves problematic, since all of these devices are unable to close the port operating the telescopic lens.
These technical challenges can compromise the wound's integrity, resulting in complications such as poor wound healing, suture failure, and port-site wound herniation, all of which will inadvertently negate the advantages of the MIS procedure. Ultimately, these complications will lead to increased pain and loss of productivity for the patient, while at the same time reducing efficiency with increased costs to the health care system in general.